Regenerative method and apparatus for liquefying natural gas



May 25, 1954 H. F. HAGEN 2,679,145 REGENERATIVE METHOD AND APPARATUS FOR LIQUEFYING NATURAL-GAS Filed Dec. 8, 1951 Invemor f ZZW @f flfzarneys Patented May 25, 1954 REGENERATIVE METHOD AND APPARATUS FOR LIQUEFYING NATURAL GAS Harold F. Hagen, Wilmette, 111., assignor to Union Stock Yards & Transit Company, Chicago, Ill., a. corporation of Illinois Application December 8, 1951, Serial No. 260,725

7 Claims.

This invention relates to improvements in method and apparatus for storing and shipping natural gas and the like and has for one object to provide a regenerative method and apparatus which will make use of the pressure of the natural gas in a well to liquefy the gas.

Another object of the invention is to provide a method and apparatus wherein gas from a well will be reduced intemperature and liquefied by the use in part of the natural pressure of the gas and by the use in part of some of the gas as a combustible to generate some of the power necessary for liquefaction.

Another object of the invention is to pass the gas under the natural pressure from the well through a work zone wherein the temperature and pressure of the gas will be lowered for the formation of wet gas. Thereafter the wet fraction of the gas will be extracted and the remaining dry gas will be recycled for further liquefaction and extraction.

Another object of the invention is to provide means whereby natural gas under natural pressure from the well will pass through a turbine doing work and generating power, the work done ultimately resulting in such reduction of pressure and temperature that a wet gas results, the wet fraction being then extracted, the remaining gas being then compressed and cooled and recirculated to do further work for the production of a further amount of wet gas.

Another object of the invention is to provide.

a method and apparatus whereby some of the power required to cool and liquefy the gas re-' sults from the reduction in the pressure of the natural gas and other of the work results from the combustion of some of the natural gas. Gas is discharged from a natural gas well at high pressure, frequently above 2000 p. s. i. a. Such gas has in the past been shipped in pipe lines. It has also been shipped at high pressure in tanks of sufficient strength to withstand the pressure but pipe lines are expensive and frequently do not reach to the point where the gas is available. The transportation of gas in tanks at high pressure, owing to the great strength and weight of tank required is especially for the shipment of large quantities of gas prohibitive in cost.

I propose to liquefy the gas at very low tem-- perature and ship and store it in tanks at atmospheric pressure, bleeding off a sufiicient amount of vaporized gas from the liquid and discharging it from the tank so as to maintain the tank at substantially atmospheric pressure.

This makes it possible to store or ship gas in substantial quantities at reasonable cost.

I propose to pass the gas from the well at natural pressure through a work zone, preferably one or more turbines where the high pressure gas will do work with resultant drop in pressure and drop in temperature. The pas sage of the gas through the work zone will be so organized that when it leaves the zone the gas is at very low pressure and instead of being a dry gas is a wet gas. By wet gas I mean a gas wherein liquid or liquefied gas is mixed with dry gas in the gaseous condition. This wet gas will be conducted to a separator where the wet fraction will be mechanically removed from the gas, the wet fraction being conducted to a storage tank, the remaining dry gas being recirculated through the work zone.

The turbine or work zone will be in a plui'ality of stages and the gas returning from the separator will be at substantially atmospheric pressure but very cold. This returning gas I propose to pass through a compression zone,

preferably comprising a plurality of compressors With a heat extractor or cooler between each compressor so that as the gases pass through the several stages of compression, its pressure is built up to a point at which it can be mixed with the gas passing from one stage to the other of the work zone and may be repassed through the work zone for the production of more wet gas.

The cold gas from the separator will be conducted in heat interchange relationship with, the compressed gas so as to reduce the tempera- The amount of gas supplied at high well pressure to the first work stage will be controlled so as to be just suflicient to compensate for the volume of gas withdrawn from the system as a liquid because it is essential that the volume of gas in the system remain constant. If conditionsrequire variation in the amount of gas admitted to the system from the well, this would result in variation in the amount of power generated especially in the low pressure stage of the turbine. Such variation will be compensated for by varying the amount of gas burned in the internal combustion turbine, the gas received from the well being also so controlled as to compensate for the amount of gas discharged as gas from the system to support combustion in the internal combustion turbine.

While I have illustrated my invention as including a high pressure and a low pressure turbine and-five compressors with=five coolers following each compressor, -.the number of turbines and compressors and coolers might be varied. While I have illustrated turbines as providing the power, other power means making use of the pressure in the gas andas a result causing cooling of the gas and other power'means than the internal combustion turbine rnightzbeusedwithout departing from the spirit of \my :invention.

My invention is illustrateddiagrammatically in the accompanying drawingythewell and the receiver being not illustrated.

Like parts are indicated by like characters throughout the specificationand drawings.

l is a conduit conveying gas under pressure froma'well to the intake side=2 of thehigh pressure turbine The-gas .passes from 2 through nozzles 4; vanes 5, nozzles 6- and vanes l on the turbine-wheelton drive shaft 9. The spent gas at substantially reduced pressure and substantially reduced temperature is discharged from the exhaust-side ill of the turbinethroughthe duct H to the duct'lZ which leads to the low pressure turbine. The cooled gas at further reduced'pressure and temperature is discharged fromtheturbine [3 through the duct I4. This gas :being now a-iwet-gas, 1that is dry gas with condensed liquefied gas in-suspension therein, isxconduoted by duct to a mechanical separator I40 'Where theliquefied gas isseparated from the dry gas, the liquefied gasgoing' through a'duct Mi to an insulated receiver J42.

The dry gasfromthe separatorreturns through the duct 15 i through the heatexchanger I B, duct H tothecornpressor wheel IS in the-first stage of compression i9. This raises the temperature and pressure of the gas; Then gastravelsxthrough theduct '23 'to the cooler 2|. This .cycle lSrIepeated through the compressor 22, cooler '23, compressor 24; cooler-25, compressorZS; cooler 21,- compressor- 28, cooler 29;

Thegasgby this sequence of compressors and coolers will be brought to such temperature-:and pressure :that when it has passed 2 through i the conduit 30 and the heat exchanger IE, it willcbe" discharged through the 'conduit 31 to meetithe gas discharged from the conduit l I,-'the"pressure of r thegas'zdischarged through conduit 3 I being the same as the pressure of the'rigas di'scharged from the conduit H. The 'gasfrom'both-sources then passes through the lowpressure turbine 13.

.As aicontinuous massof'gas passesfthrough both systems; the 'drytgas continues to recirculate,

the wet gas formedby this cycling being-gradually deposited and left in the receiver, such process continuing until the receiver is filled with a suitable amount of .coldliquid gas.

The compressors raisethe temperature of thegas; It-isessentialthat'the heat generatedby the compressors be removed --'fromi the gas. The coolers 2|, 23, 25,f2'l',"an'd 22s,: arecooled' by water or other suitable coolant entering through the pipestiand 33 and'discharging' through the pipes 34.and35.

.The shaft 9 carries thecompressor wheelsand the additional powerneeded to operate the compressors comes from. a gas turbine 36. The gas to supply such turbine. is discharged through .the

' called: a regenerative process.

duct 31 from the first stage of compression. Gas is burned in the gas turbine in the usual manner well known in the art, the turbine assisting in driving the shaft 9 to generate the power required to operate the compressors.

I43 indicates a control valve to control the rate of flow ofgasirom thewell. lt may be manually controlled or automatically; the details of this valve and control forming no part of this inxvention are not illustrated, except that lever M4 may be connected to any suitable control means. 'Thepuseandoperation of the invention are as follows andflows throughthe; low pressure turbine. The:

gas going through the low pressure turbine in turn delivers power-to-the shaftof the. apparatus, as a result is cooled and exhausts in thecondition at atmospheric] pressure. -It then goes to the receiver and theliquidis-deposited.- Theqcold dry gas is broughtbach from: the receiver through aheat exchanger where the recirculatedzgasiscooled on its way. to .the .low pressure turbine. The ;gas .from :the receiver having been heated by the transfer of heat fromltherecirculated'gas,-

then is passed into; the: compressor units. The-gas passes rfrom-each compressor -.stage through a" cooler to the nextacompressor. Thezcompressor cooler system will-.deliventhe .compressedgas, for

example, to the regenerative zheatr-exchanger. at

a stemperaturerabove the:temperature of the exhaust from the high pressure turbine. .The'

regenerative heat exchange will-bringzthe -tem-' perature of the compressed gas to -a 'lower temperature and the -:cooled gas :will :mix with the exhaust from .the high pressure turbine and this mixture will pass through th'erlow pressure turbine .for liquefaction.

:An: outstanding: f eature of"- this arrangement is in connection :withrthe'gas'1turbinewhich is also oncthesamedine of shafting'. The compressors takeiconsiderably;more powertthani thehighpressure turbine and theilowpressure. turbine already' mentioned. can develop. This; additional 'poweris supplied-bye gasturbine burningsomeof the gas. The gas for thissturbine willsbe taken-fromthe': circulating isystemxafter on-e of the: stages of :the compressor 1 units :as desired. .As showngthe gas is taken 'atterrthe first-stagerat Lior example 60 p.s."i. .a. and'delivered to the gas-turbinebut the :'as"liorv the turbine has been':.put through the regenerativeicycle. and theamountof gas i liqueifieid, which is aipercenta'ge; is' 'therebyincreased' More gas goesithroug-h'the'low' pressure turbine than is handled by the main portion orthe ccmpressor unit. Theresult of this 'will "bea bigger casezif the high pressure and lowpressure turbine units were driven by an electric motor for example. 2

In a sense, if We limit our thinking to one cycle of:recirculation the gas used inthe gas turbine is :waste' gas. In order 'further tolillu'strate the: conception; if there -iwasav sale. for gas. in l a neighboring community, all of the a gas not-:- liquefiedwcouldrbe delivered from :therreceiverf: to the community gas; mains. "Lam takingw;ad-,z ;z

vantage of this idea to use the gas for my own necessary-power.

. From the receiver of the liquefaction plant the liquid methane may flow into tanks in a barge which are so-to-speak the final receiver and such bargemay thereafter be propelled to any suitable point at whichthe liquefied cold gas may be needed.

I have used the expression multi-stage turbine. Usually all turbines are multi-stage but that expression in this particular instance is intended to means a turbine wherein one stage at least discharges gas out of the turbine before the gas is returned to the turbine for the next stage. I have shown a high pressure turbine 3 and a low pressure turbine i3. It is the high pressure stage and the low pressure stage that I am referring to when I use the term multistage in this connection. The high pressure turblue is smaller than the low pressure turbine. They might be in the same housing but the gas does not go directly from the high pressure stage or stages to the low pressure stage or stages but the exhaust from the high pressure turbine is mixed with an additional supply of gas so that they pass together through the low pressure turbine.

One example of a device such as this would be a situation where the gas supplied to the high pressure was at 2500 pounds pressure. The gas supplied to the low pressure turbine would be at 1000 pounds pressure. The relationship between the weights of gas passing through the two turbines might be that the low pressure turbine would receive twenty-five percent of its gas from the exhaust or the high pressure turbine while seventy-five percent of the gas would be recirculated and supplied to the low pressure turbine from the condensing system. Any weight, for example, we might have five hundred pounds of gas per minute entering the high pressure turbine, would be joined by 1500 pounds of gas per minute recirculating through the system and so going through the low pressure turbine.

The pressure drop and work done in the low pressure turbine results in liquefaction even as the gas is passing through the blades but due to a time lag most of the liquefaction takes place after the gas has been discharged from the blades into a space or receiver at atmospheric pressure.

Only a small part of the gas coming from the Well is bled off to supply the combustion turbine. It is bled off after, not before, it is circulated through the high pressure and low pressure turbines and the gas separator because by that arrangement, the pressure value of the gas from the well is not lost and the cooling eifect of all the gas is made available before any combustion takes place.

I claim:

1. The method of liquefying natural gas which includes discharging the gas from a gas well at substantially natural well pressure, causing the gas to expand and do work in a primary work zone, with resultant cooling, mixing the spent gas from the primary work zone with an additional supply of gas, at substantially the same pressure, causing the resultant mixture to expand and do work in a secondary work zone, with resultant further cooling and liquefaction of some of the gas, removing the liquid from the dry gas, 'compressiong the dry gas, cooling it and using it to provide the additional supply of gas for recirculation through the secondary work zone with the spent gas from the primary work zone.

2; The method of liquefying natural gas which includes discharging the gas from a gas well at substantially natural well pressure, causing the gas to expand and do work in a primary work zone, with resultant cooling, mixing the spent gas from the primary work zone with an additional supply of gas, at substantially the same pressure, causing the resultant mixture to expand and do work in a secondary work zone, with resultant further cooling and liquefaction of some of the gas, removing the liquid from the dry gas, compressing the dry gas, cooling it and using it to. provide the additional supply of gas for recirculation through the secondary work zone with the spent gas from the primary work zone, controlling the rate at which gas is discharged'from the well to compensate for the liquid removed from'the dry gas.

3. The method of liquefying natural gas which includes discharging the gas from a gas well at substantially natural well pressure, causing the gas to expand and do work in a primary work zone, with resultant cooling, mixing the spent gas from the primary work zone with an additional supply of gas, at substantially the same pressure, causing the resultant mixture toexpand and do work in a secondary work zone, with resultant further cooling and liquefaction of some of the gas, removing the liquid from the dry gas, compressing the dry gas, cooling it and using it to provide the additional supply of gas for recirculation through the secondary work zone with the spent gas from the primary work zone, burning some of the dry gas to furnish power to compress the dry gas.

4. The method of liquei'ying natural gas which includes discharging the gas from a gas Well at substantially natural well pressure, causing the gas to expand and do work in a primary work zone, with resultant cooling, mixing the spent gas from the primary work zone with an additional supply of gas, at substantially the same pressure, causing the resultant mixture to expand and do work in a secondary work zone, with resultant further cooling and liquefaction of some of the gas, removing the liquid from the dry gas, compressing the dry gas, cooling it and using it to provide the additional supply of gas for recirculation through the secondary work zone with the spent gas from the primary work zone, using the cold dry gas to cool the compressed dry gas before it is mixed with the spent gas from the primary work zone.

5. In combination, a high pressure and a low pressure turbine rotor, housings therefor, valve controlled means for supplying high pressure gas to the intake side of the high pressure rotor housing, means for conducting spent gas from the exhaust side of said housing to the intake side of the low pressure rotor housing, a liquid separator, means for conducting gas from the exhaust side of the low pressure rotor housing to the separator, means for withdrawing liquid gas from the separator, a rotary compressor, means for conducting dry gas from the liquid separator to the intake side of the rotary compressor, a

cooler, means for conducting gas from the discharge side of the rotary compressor through the cooler to the intake side of the low pressure rotor housing.

6. In combination, a high pressure and a. low pressure turbine rotor, housings therefor, valve controlled means for supplying high pressure gas to the intake side of the high pressure rotor hensing, means for conducting spent gas from the exmust: side :ofassaid 'housinglto' zthemntzke side of the-low pressurerrotor:housingaafliquids'separator; meansiioreconducting gasa'from the exhaustf'side ofi the iow, pressureiroter housingztoftherseparator, means;forwithdrawingiliquid gas from the separatomasrotary :eompresson'means for :conducting dryrgas from .-the liquidzzseparator to .the intake siderefuthez rotarytrcompressor;:ascooler; means i or conducting-gas .from the discharge 'sside of the rotary; compressor: through athe cooler :to the .intake-:sidev of :the view pressure actor-"housing, a heatcexchanger:through=which cold gas" from'the lieu-id separatortpasses 'on'its Way to the rotary compressor tozadditienallycool. the :gas on its-way from the'eoolersziozthe intakeiside of the low'pressniteuotor'housingi 7:.:Im?combination,1a 1 high .pressureand .ta' low pressure turbine rotor, housingsiztherefor,valve controlled :means for supplying high pressure asttoathe tintake:side-' of therhi'gh apres'sure rotor housing, amean's i for :con'ducting spent :gas .1 from theexhaustsidaofcsaidrhousingato therintake side ofcthe:iowapressurezrotor housing,- aa liquid separator; means ior conducting gasifmm thesexlraust side of the low pressure rotorr'zhousing 'ito the se'p arator, meansi'for" withdrawingdiquidsgasrfiom the separator, .a" rotary eompressor; means its: conducting dry gas fromizthe liquid separatorfto the-intake side of therotarycompressoni'aicooler. means for eonductingygasfromithe"dischargecsitie of the rotary compressor through the cooleritmthe intake" side ofthe lowlpressure-irotorhousing, a. prime mover adapted to'burn: some'ofathe dry-gas discharged from the separator to furnish power so operate the compressori ands a driving' connection between the turbinerotors atheeompressoraand the prime mover.

Referenees Cited in the file of this patent UNITED 'STATESAPA'I'ENTS' Number I Name Date I "642,505 "Thrupp r. Jan. 30, I900 "20i1,551 Hasche" "Aug'. "13,1935

"2,520,862 *Swearing'en "Aug.'-"29} 1950 

